A number of texts cover the principles of acquisition of marine seismic data (e.g., Sheriff and Geldart, 1995; Ikelle and Amundsen, 2005). There are several configurations of source and receiver distributions; those commonly used for petroleum exploration are (1) towed-streamer acquisition, where sources and receivers are distributed horizontally in the water column near the sea surface; (2) ocean-bottom seismic (OBS) acquisition, where the sources are towed in the water column and the receivers are on the seafloor; and (3) vertical-cable (VC) acquisition, where the sources are towed near the sea surface as in towed-streamer and OBS acquisition but the receivers are distributed in the water in a vertical array.
The receiver systems in these configurations are (1) normally hydrophones but possibly also vertically oriented geophones for towed-streamer acquisition; (2) hydrophones and three-component (3-C) geophones or accelerometers for OBS acquisition; and (3) hydrophones for VC acquisition. In the OBS experiment, the geophones or accelerometers are in contact with the seafloor so that the recording of shear waves is enabled. If the horizontally oriented geophones or accelerometers were not in contact with the seafloor, they would produce a measurement of the horizontal derivative of the pressure field.
The benefits of 2-C streamers are well known (Berni, 1984; Ruehle, 1984; Amundsen, 2001; Carlson et al., 2007). When introduced in 2007 by PGS, the geostreamer provided a step change in marine seismic acquisition. The geostreamer is equipped with both hydrophones and vertically oriented geophones so that, among others, up/down wavefield decomposition or receiver-side deghosting can be achieved, thereby enabling the acquisition of broadband seismic data.
Three-dimensional (3-D) up/down decomposition of the wavefield in the water column requires the proper measurement of both pressure on a hydrophone and vertical component of particle velocity on a vertically oriented geophone. To date, such measurements are not available in towed streamer acquisition due to the large cross-line separation between streamers, which typically is between 50-100 m.
Robertsson et al. (2006, 2008) state that 3-C geophone measurements would bring significant benefits to towed-marine seismic data if recorded and processed in conjunction with the pressure data. They show that particle velocity measurements can increase the effective Nyquist wavenumber by a factor of two or three, depending on how they are used.
Singh et al (2009) propose seismic acquisition using a plurality of streamers, with a streamer having a plurality of compact clusters of hydrophones and/or particle motion sensors. Cluster means a plurality of sensors of the same type that are used together. The streamer is adapted to provide gradient measurements of pressure with the objective to provide improved methods of interpolating seismic data between adjacent streamers.